1. Field of the Invention
This invention relates to a process of producing a low-water suspension which consists mainly of fine-grained brown coal and oil and is to be hydrogenated in the presence of a high-hydrogen gas under a pressure of 100 to 400 bars and at a temperature of about 300.degree. to 500.degree. C.
2. Discussion of Prior Art
It is known that various coals, inclusive of brown coals, can be hydrogenated and the hydrogenated products can be processed to produce motor fuels. A detailed description of this technology has been given by W. Kronig in his book "Die katalytische Druckhydrierung von Kohlen, Teeren und Mineralolen" (1950), Springer-Verlag, Berlin-Gottingen-Heidelberg. More recent developments have been described in U.S. Pat. Nos. 3,745,108; 3,660,269; and 3,635,814. In the known processes, a catalyst is used or is not used in the hydrogenating zone. Most processes using no catalyst rely on the catalytic activity of metallic components of the coal. Coal to be hydrogenated must be very finely divided so that it presents a large surface area to the hydrogen. A catalyst which is employed must also be finely divided and must be mixed with the coal.
The hydrogenation of brown coal is adversely affected by its high water content, which is usually in the range of 35 to 70% by weight of water related to the total weight of the water-containing brown coal. That water content must be considerably reduced, below 10% by weight, before the hydrogenation.
It is an object of this invention, therefore, to provide a process for the preparation of a brown coal-oil suspension where the brown coal has a reduced water content and can be readily employed in reactions with hydrogen. It is a further object of this invention, therefore, to provide a simple and efficient method for the reduction of the water content of brown coal-oil suspensions.